This invention relates to an oxide glass capable of exhibiting a long lasting afterglow and photostimulated luminescence, whereby energy can be accumulated by radiation excitation, for example, by xcex3-rays, X-rays, UV-rays, etc., light emission can be continued for a long time even after stopping the excitation, so that the oxide glass can be used as a phosphorescent material for night illumination or night signal, and furthermore, photostimulated luminescence can be exhibited by irradiation of visible rays or infrared rays, which is useful for confirming an infrared laser or controlling an optical axis of a laser beam, so that recording or reproducing of xcex3-rays, X-rays or UV-rays images can be effected, and which can be used as an optical recording material capable of reading and writing.
Phosphorescent materials or photostimulated luminescence phosphor using rare earth elements have widely been used up to the present time. As a phosphorescent material, there can practically be used SrAl2O4:Eu2+, Dy3+, etc. and as a photostimulated luminescence phosphor, there has already been developed BaFBr:Eu2+, etc. These are opaque materials only exhibiting superficial phosphorescence, generally obtained by coating a suitable carrier with a powdered phosphorescent material or photostimulated luminescence phosphor.
On the other hand, a glass capable of exhibiting a photostimulated luminescence without coating a photostimulated luminescence phosphor has been disclosed in JP-A-9-221336. In addition, Japanese Patent Application Nos. 346362/1997, 130344/1998 and 187341/1998 respectively disclose obtaining phosphorescent glasses of SiO2xe2x80x94B2O3xe2x80x94ZnOxe2x80x94Tb2O3 system, GeO2xe2x80x94ZnOxe2x80x94Na2Oxe2x80x94Tb2O3 system and SiO2xe2x80x94ZnOxe2x80x94Ga2O3xe2x80x94Tb2O3 system.
In the case of coating a powdered phosphorescent material or photostimulated luminescent phosphor, dispersion of the coating thickness or peeling-off of the coated surface occurs whereby to cause light and shade of the phosphorescence. Furthermore, in order to increase the emission intensity, it is required to coat a phosphorescent material or photostimulated luminescence phosphor with a larger thickness, but the coating is limited by increase of opaqueness thereof. Since a phosphorescence emitted from a grain boundary in the phosphorescent material or photostimulated luminescence phosphor is scattered, furthermore, no clear image can be obtained.
A photostimulated luminescent glass described in JP-A-9-221336 utilizes Ce3+ or Eu2+ as an active ion for emission. In order to obtain these active ions, it is necessary to add a reducing agent or to melt in a reducing atmosphere. Furthermore, observation of the emission is difficult because of being UV light or blue light.
The present invention has been made to solve the problems of the prior art, as described above, and aims at providing an oxide glass capable of exhibiting a long lasting afterglow and photostimulated luminescence of green or red emitted light readily observable, which can be melted without using any reducing agent or reducing atmosphere by utilizing Tb or Mn as a phosphorescent or luminescent agent.
The present invention, developed under this situation, provides:
(1) an oxide glass capable of exhibiting a long lasting afterglow and photostimulated luminescence by excitation with radiation such as xcex3-rays, X-rays, UV-rays, etc. having a constitutional composition comprising, at least, gallium oxide (Ga2O3) or aluminum oxide (Al2O3), alkali metal oxide or alkaline earth metal oxide and boron oxide (B2O3) or silicon oxide (SiO2) or zinc oxide (ZnO) in addition to terbium oxide (Tb2O3) or manganese oxide (MnO) as a phosphorescent agent.
Specifically, the present invention relates to (2) an oxide fluorescent or phosphorescent glass capable of exhibiting a long lasting afterglow and photostimulated luminescence, as described in the above (1), which is represented, in terms of atoms for making up the glass, by the following chemical composition (mol %):
(3) An oxide fluorescent or phosphorescent glass capable of exhibiting a long lasting afterglow and photostimulated luminescence by excitation with radiation such as xcex3-rays, X-rays, UV-rays, etc., as described in the above (1), which is represented, in terms of atoms for making up the glass, by the following chemical composition (mol %):
According to the above described construction, energy can be accumulated by radiation excitation, for example, by xcex3-rays, X-rays, UV-rays, etc., light emission can be continued for a long time even after stopping the excitation, and furthermore, photostimulated luminescence can be exhibited by irradiation of visible rays or infrared rays.